An horticultural engineer, he was director of the Montreal Botanical Gardens from 1980 to 1994.
Bourque was the mayor of Montreal, Quebec from 1994 to 2001 (as the leader of the Vision Montreal party).
Bourque proved eccentric and sometimes controversial as mayor. Known as a greenspace aficionado, he supported the creation of parks, implemented tree-planting initiatives, as well as creating Eco-Centres (reusable materials) and Eco-Quartier program (recycling). He was also responsible for the revitalization of many important districts of Montreal (Saint Catherine Street, Old Montreal and the Multimedia City) as well as the reopening of the Lachine Canal.
In 1998, responding to critics who denounced him for not fighting poverty, he spent the night with a working-class family. He was also well known for his close ties to minority "cultural communities". Bourque directed the city's public service to make an intercultural calendar for meeting scheduling.
At one time, Bourque was a moderate supporter of the sovereigntist Parti Québécois. Bourque's successful attempt, with provincial support, at merging all of Montreal’s 28 municipalities into a megacity of 1.8 million people and 27 boroughs cost him the election in 2001. Although he gathered a majority of votes in what was until then the city of Montreal, protest votes against the very principle of the merger in the former suburbs ensured a solid victory to his rival Gérald Tremblay. Pierre Bourque still sat on the municipal council, taking his running mate Kettly Beauregard's spot.
He subsequently attempted to enter provincial politics, running as an Action démocratique du Québec candidate in the 2003 Quebec election, but was defeated. Bourque finished third, behind then minister Diane Lemieux (Parti Québécois) and the Liberal candidate. He then returned to municipal politics, but was unable to win re-election as mayor.
Bourque lost for a second time to incumbent-mayor Gérald Tremblay in his fight to regain control of city hall in the Montreal municipal elections held on 6 November 2005, this time by a 74,646 vote margin. The voter turnout was less than 40%, among the lowest in Montreal's history.
On 3 May 2006, Bourque stepped down as Leader of the Opposition on Montreal's city council.
He currently runs a company called Constellation Monde Inc. which operates in China. Bourque wants to develop further economic links between the country and the province.1992 – Professional Citation, American Public Gardens Association.
1993 – National Order of Quebec.
2007 – Order of the Rising Sun, Gold Rays with Neck Ribbon (Japan).